This invention relates to a pneumatic pipe plug typically used to block or divert the flow in municipal or commercial pipe. In particular, this invention relates to a pipe plug having a molded surface designed to resist slippage when installed and the method of manufacturing the plug.
A pneumatic pipe plug operates by inflating an expandable bladder which expands against the inside wall of the pipe. Typically, the pipe can range from inches to many feet in diameter. The pneumatic pipe plug remains in place by the frictional forces generated between the expanded bladder and the inside wall of the pipe. As used herein, the term “pipe plug” includes a flow diverter in which the normal flow of the fluid in the pipe is blocked and directed to a smaller flow through conduit and typically redirected to a recovery or disposal location through a connected hose.
The pipe plug is typically used in an environment that is unpredictable and may be critical to the safety of workers, for example, in a municipal sewer pipe line that is blocked with a pipe plug to allow repair men to enter and repair a segment of pipe. In such environments, the pipe plug must be versatile, rugged and highly resistant to failure. In order to meet this challenge, conventional pneumatic pipe plugs are in part hand fabricated which adds substantially to the resultant cost. Problems in fabricating pipe plugs for larger diameter pipe are compounded by the aggregate forces applied to the plug from even moderate fluid pressures. In typical drainage pipe systems, the pipe plug must withstand a ten foot water head and similar pressures from fluids and other environments are expected to be encountered.
In order to achieve greater uniformity in the manufacture of pipe plugs, particularly in larger diameters, mechanized fabrication and assembly has largely replaced hand fabrication and assembly. In addition to a uniform appearance, the mechanically manufactured pipe plug has a more consistent structural integrity and predictable reliability. Since an inflated pipe plug or flow diverter may be all that separates a worker from a flow of water, an unexpected failure should be avoided. Mechanizing and automating the manufacturing tasks reduce the unit cost and standardize performance.
In fabricating a pneumatic pipe plug the interconnection of the pneumatic bladder and the rigid end structure of the plug is problematic. Customarily, the expandable bladder is formed with an end that is custom formed and wrapped over and around rigid end plates which include anchor means to control the pipe plug, and fittings to provide for supply of air or other gas to the pipe plug during inflation.
In my U.S. Pat. No. 6,481,465, issued on Nov. 19, 2002, entitled, “Compressed-Ring Pneumatic Pipe Plug” incorporated herein by reference, an improved construction of a pipe plug is described. In that reference, the pipe plug has an expandable bladder in the form of an elongated annulus with ends that are connected to disk-like end caps by outer rings that slip over the bladder ends and end caps, and are compressed by swaging. This mechanical means of coupling the elastic bladder to the rigid end caps is both cost efficient and effective.
It is the object of this invention to improve the fabrication process for the pneumatic bladder such that the resulting product is uniform in both appearance and performance and is enhanced with a novel rib and textured band gripping surface. The enhanced gripping surface is formed by a curing mold and improves the resistance to slippage when the pipe plug is installed and expanded. In addition, the mold-formed surface of the pipe plug enhances the ability to inspect the component for quality control of the finished product.